The present disclosure relates, in various embodiments, to semiconducting polymers suitable for use in electronic devices, such as organic thin-film transistors (“OTFT”s). The present disclosure also relates to semiconductor layers produced using such polymers and electronic devices containing such semiconductor layers.
Thin film transistors (TFTs) are fundamental components in modern-age electronics, including, for example, sensors, image scanners, and electronic display devices. TFT circuits using current mainstream silicon technology may be too costly for some applications, particularly for large-area electronic devices such as backplane switching circuits for displays (e.g., active matrix liquid crystal monitors or televisions) where high switching speeds are not essential. The high costs of silicon-based TFT circuits are primarily due to the use of capital-intensive silicon manufacturing facilities as well as complex high-temperature, high-vacuum photolithographic fabrication processes under strictly controlled environments. OTFTs offer not only much lower manufacturing costs, but also appealing mechanical properties such as being physically compact, lightweight, and flexible.
OTFTs are generally composed of a supporting substrate, three electrically conductive electrodes (gate, source and drain electrodes), a channel semiconductor layer, and an electrically insulating gate dielectric layer separating the gate electrode from the semiconductor. The channel semiconductor is in turn in contact with the source and drain electrodes. The materials used to make the OTFTs, and the interfacial properties between various layers of semiconductor, dielectric, and electrodes will affect the performance of the OTFTs. Accordingly, a great deal of recent effort has been devoted to improving the OTFT device performance through new semiconductor materials design, improvement of semiconductor ordering, and optimization of semiconductor and dielectric interface, etc. For examples, see U.S. patent application Ser. Nos. 10/636,389 and 11/315,785 [20041557-US-NP, XERZ 2 01095], the disclosures of which are herein incorporated by reference in their entirety.
Most semiconductor materials for TFTs suffer from their insolubility in solvents suitable for liquid processing. They may also be extremely sensitive to air and light. In order to combat these and other difficulties, organic polythiophenes, such as PQT, have been developed. See U.S. Pat. Nos. 6,621,099; 6,770,904; 6,872,801; and 6,897,284; the disclosures of which are herein incorporated by reference in its entirety. PQT 12 is a printable high-mobility semiconductor suitable for use in OTFTs. It has the chemical structure shown below:
wherein n is the degree of polymerization and is from about 5 to about 5,000. PQT 12 provides mobility up to 0.2 cm2/V·sec and has a current on/off ratio of 108. These attributes are adequate for many electronic applications, such as the backplanes of displays, but not for others. Consequently, there is a need for improved semiconductor materials.